In many household and other non-industrial situations, it is necessary or desirable to sterilize or disinfect water as well as certain objects. For example, with infants up to six months of age, it is generally recommended to disinfect or sterilize the formula fed to the infant as well as the bottles including the nipples which are used during feeding. As another example, when camping many sources of drinking water, e.g. lakes, streams, etc. may be contaminated with potentially harmful organisms. Similarly, international travellers may be susceptible to microorganisms found in water in various locations.
The term "sterilization" generally denotes the process of eliminating all viable microorganisms from a material, including the spores of the microorganism. In contrast, the term "disinfection" generally refers to the process of destroying, or sometimes merely reducing, the potential infectivity of the material and does not necessarily imply the removal of all viable microorganisms and their spores.
At the present time, the most commonly employed household or other non-industrial methods of disinfection or sterilization are the use of heat and of chemical agents. In the case of heat, the most commonly employed household or non-industrial application uses boiling water. In the case of chemical agents, the most commonly utilized techniques use chlorine gas generating solutions and tablets. Thus, for example in the case of drinking water when camping, potable water is produced either by boiling the water for up to twenty minutes or by adding a chlorine gas generating tablet to the water. In the case of baby bottles, they are generally disinfected by being maintained in a boiling water bath for from five minutes up to about twenty minutes.
The use of boiling water has numerous disadvantages as it can be a tedious or inconvenient procedure, because of the amount of time necessary to disinfect the water. The use of boiling water may also be somewhat dangerous because of the potential for scalds from boiling water baths. Additionally, the use of boiling water for disinfection of baby bottles may result in deterioration of the nipples and clouding of the plastic bottles caused by tiny cracks which may harbor microorganisms which may be difficult to remove.
It is often believed that the use of boiling water results in sterilized water. However, in fact the water may often be only disinfected and not sterilized. For instance, depending upon how long a period of time the water is boiled, some microorganisms may not be killed or inactivated. Boiling water will also generally not kill or inactivate all of the spores of such microorganisms which generally remain viable at about 100.degree. centigrade, the maximum temperature of boiling water under normal conditions. In some applications, there is the potential of the spores continuing to cause some health problems. The spores can germinate to form viable organisms, which if present in small numbers are generally not a major problem. However, if the disinfected solution, for example baby formula, is maintained for extended periods at certain temperatures even a small number of organisms can rapidly multiply and may result in potentially serious illnesses.
There have been attempts, such as the chlorine gas generating tablet described above, to develop cold sterilizing and disinfecting methods which can be used in household or other non-industrial applications. These methods rely on the use of various chemical agents, but still such methods suffer from a number of disadvantages. One such method, for example, requires the use of sodium hypochlorite and other chlorine gas generating solutions. These solutions result in the release of free chlorine gas into the water, which in certain applications can present problems. Chlorine gas is objectionable since in aqueous solution it forms hypochlorous acid, it has a very sharp odor in concentrations as low as 3.5 p.p.m., it is extremely corrosive and it forms toxic and possibly carcinogenic organohalogen compounds, while causing irritation of the pulmonary mucosa. In order to avoid most of these problems the water must be left for a sufficient period to allow the chlorine gas to dissipate. When using these methods with baby bottles, the bottles and nipples are generally rinsed afterward to remove any traces of chlorine and other by-products, with the result that the bottle can be reinfected, thereby defeating the disinfection process.
A number of halogen containing compounds, such as, for example, chlorine dioxide, bromine oxide, bromine chloride, monochloroamine, bromic acid, hypochlorous acid, chlorates, chlorites, hypochlorites, iodine monochloride, iodine trichloride and iodine monobromide among others, are known to be effective disinfecting and sterilizing agents if applied in the proper concentrations. In particular, chlorine dioxide has been used for many years in treatment of municipal water supplies and has recently been demonstrated to be effective as a medical and dental equipment sterilizer, as a disinfectant and deodorizer for beds, as a fungicide, as a toothpaste additive used to prevent dental caries, and as a mouthwash additive.
Chlorine dioxide has been demonstrated to result in the destruction of many microorganisms and their spores at strengths as low as 0.75 p.p.m., as little as 1 p.p.m. of chlorine dioxide in solution killing or inactivating 99,999 of 100,000 Escherichia coli bacteria upon contact for five minutes. Chlorine dioxide has also been shown to be effective in inactivating among others, bacteria such as, Bacillus anthracoides, B. subtilis, B. cereus, B. stearothermilus, B. mesentericus, B. megatherium, Clostridium perfringens, Erberthella typhosa, Haemophilus influenzae, Shigella dysenterie, Salmonella paratyphi B, Salmonella typhosa, Pseudomonas aeruginosa and Staphylococcus aureus; protozoa and algae such as Naegleria gruberi; and viruses such as HTLV-III, poliovirus, echovirus, Coxsackie virus, Herpes simplex virus, Newcastle disease virus, Sendaivirus, Vaccinia virus, bacteriophage f2, coliphage and phage .phi.X 174.
However, some of such halogen containing compounds, such as chlorine dioxide, bromine oxide, bromine chloride and monochloroamine, among others, are generally unstable and there have been a number of problems associated with such instability. In particular, the use of chlorine dioxide is somewhat problematic because at 25.degree. centigrade it exists as a yellow gas which is explosive and may detonate under certain conditions. Thus, chlorine dioxide, being readily soluble in water, is usually stored as an aqueous solution at a low temperature to reduce its instability. Such halogen containing compounds, (e.g. chlorine dioxide, bromine oxide, monochloroamine and bromine chloride, and in particular, chlorine dioxide), however, even in solution, remain generally unstable, in the sense that they have relatively high rates of chemical breakdown or dissociation, particularly in the presence of light. These high rates of chemical breakdown or dissociation render them inefficient and sometimes totally ineffective.
In order to reduce the dissociation of such compounds in solution and take advantage of their excellent sterilization properties, there have been attempts either to provide stable solutions of such compounds or to generate such compounds at their place and time of use. For industrial or commercial applications having the necessary equipment and other resources, the chlorine dioxide is generally produced and used immediately. With household or other non-industrial applications it is not cost effective, feasible or safe to do this. There have thus been attempts to provide stable chlorine dioxide solutions as evidenced by U.S. Pat. Nos. 3,123,521, 3,585,147 and 3,591,515 among others. In most of these situations, the chlorine dioxide is provided by releasing the gas by acidification of solutions in which the chlorine dioxide is made more stable by the addition of a peroxygen or boron compound. While this does result in an increase in the effective shelf life of such chlorine dioxide generating solutions, there is still significant spontaneous breakdown of the chlorine dioxide and, consequently, the sterilizing capacity of the solution is rapidly diminished.
In view of problems, such as noted above, satisfactory methods of storing and/or transporting such halogen containing compounds which allow them to retain their disinfecting or sterilizing properties have not been readily available. The result has been that it has thus not always been possible to utilize to its full potential the excellent disinfectant and sterilizing capability of chlorine dioxide and other such unstable halogen containing compounds, particularly in household and other non-industrial applications.